One type of wireless communication system relies upon an architecture in which multiple transmit antennas and multiple receive antennas are used. Such architectures are referred to as “multiple-input, multiple-output” or “MIMO” wireless systems. MIMO wireless systems have grown in popularity as such systems provide increased data throughput and increased range without an increase in bandwidth usage.
In general, a MIMO transmitter transmits a signal that includes more than one spatially multiplexed data stream. The number of data streams in the transmitted signal is equal to the number of transmit antennas used by the MIMO transmitter. Each data stream carries independent data. A MIMO receiver recovers each data stream. One type of MIMO receiver utilizes “sphere detection” to recover the data streams. Sphere detection is a class of near-maximum likelihood processing techniques for spatial multiplexing MIMO wireless systems. In general, sphere detection simplifies detection complexity typically involved in optimum maximum-likelihood detection techniques and provides comparable performance in terms of bit error rate (BER).